Many viral infections show seasonality, with surges often occurring in cooler months. This phenomenon has been observed with SARS-CoV-2, the virus responsible for COVID-19, as the number of cases in the northern hemisphere has surged as outside temperatures have plunged. Findings from a new study indicate that SARS-CoV-2 particles remain infectious longer in cooler temperatures.

SARS-CoV-2 is a type of human coronavirus. At least seven coronaviruses are known to infect humans, including SARS-CoV-1 (which causes severe acute respiratory syndrome, or SARS) and MERS-CoV (which causes Middle East respiratory syndrome, or MERS). SARS-CoV-2 is highly virulent and requires novel strategies for its study, such as virus-like particles – multiprotein structures that mimic the parent virus but lack the viral genome.

The authors of the study used atomic force microscopy to observe how well the virus-like particles withstood environmental changes. They applied the virus-like particles to a glass surface and then exposed them to different temperatures (ranging from 71° F to 93° F) in humid and dry conditions.

They found that exposure to warm temperatures (93° F) for as little as 30 minutes caused the outer structure of the virus-like particles to break down. However, the particles' integrity was not affected at cooler temperatures (71° F). The effects of warm temperatures were greater in dry conditions than in humid ones.

These findings suggest that SARS-CoV-2 remains infectious longer in cooler, drier environments, such as those encountered outside during winter months or indoors and underscore the importance of adherence to public health guidelines for washing hands, wearing masks, and distancing whenever possible.

• Link to full study.